Sam Tobin-Hochstadt wrote:
I'm puzzled by the behavior of the below program. In particular, `get' doesn't work, but `get2' does, even though the only difference is the phase at which they're executed. `get' produces the certificate error:compile: access from an uncertified context to unexported variable from module: 'm1 in: x Is there a way around this? Working at phase 1 has become inconvenient for me. #lang racket/load (module m1 racket (define x 1) (define-syntax (m stx) #'(list x)) (provide m)) (module m2 racket (require 'm1 (for-syntax syntax/parse)) (define-syntax (get stx) (syntax-parse stx [(_ nm) (with-syntax ([(app lst val) (local-expand #'(m) 'expression null)]) #'(define nm #'val))])) (define-syntax (get2 stx) (syntax-parse stx [(_ nm) (with-syntax ([(app lst val) (local-expand #'(m) 'expression null)]) #'(define-for-syntax nm #'val))])) (get2 z)) (require 'm2)
Replace #'val with (quote-syntax val). Syntax (#') checks every identifier in its template to see if it's a pattern variable. That check counts as a reference, which is prohibited in this case by the certificate system.
The reason get2 works is that x isn't bound at phase 1, so the access control check doesn't kick in.
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